MERTK inhibition induces polyploidy and promotes cell death and cellular senescence in glioblastoma multiforme

Alexandra Sufit, Alisa B. Lee-Sherick, Deborah Deryckere, Manali Rupji, Bhakti Dwivedi, Marileila Varella-Garcia, Angela M. Pierce, Jeanne Kowalski, Xiaodong Wang, Stephen V. Frye, H. Shelton Earp, Amy K. Keating, Douglas K. Graham

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Abstract

Background: MER receptor tyrosine kinase (MERTK) is expressed in a variety of malignancies, including glioblastoma multiforme (GBM). Our previous work demonstrated that inhibition of MERTK using RNA interference induced cell death and chemosensitivity in GBM cells, implicating MERTK as a potential therapeutic target. Here we investigate whether a novel MERTKselective small molecule tyrosine kinase inhibitor, UNC2025, has similar anti-tumor effects in GBM cell lines. Methods: Correlations between expression of GAS6, a MERTK ligand, and prognosis were determined using data from the TCGA database. GBM cell lines (A172, SF188, U251) were treated in vitro with increasing doses of UNC2025 (50-400nM). Cell count and viability were determined by trypan blue exclusion. Cell cycle profiles and induction of apoptosis were assessed by flow cytometric analysis after BrdU or Po-Pro-1/propidium iodide staining, respectively. Polyploidy was detected by propidium iodide staining and metaphase spread. Cellular senescence was determined by β-galactosidase staining and senescence-associated secretory cytokine analysis. Results: Decreased overall survival significantly correlated with high levels of GAS6 expression in GBM, highlighting the importance of TAM kinase signaling in GBM tumorigenesis and/or therapy resistance and providing strong rationale for targeting these pathways in the clinic. All three GBM cell lines exhibited dose dependent reductions in cell number and colony formation (>90% at 200nM) after treatment with UNC2025. Cell cycle analysis demonstrated accumulation of cells in the G2/M phase and development of polyploidy. After extended exposure, 60-80% of cells underwent apoptosis. The majority of surviving cells (65-95%) were senescent and did not recover after drug removal. Thus, UNC2025 mediates antitumor activity in GBM by multiple mechanisms. Conclusions: The findings described here provide further evidence of oncogenic roles for MERTK in GBM, demonstrate the importance of kinase activity for MERTK tumorigenicity and validate UNC2025, a novel MERTK inhibitor, as a potential therapeutic agent for treatment of GBM.

Original languageEnglish (US)
Article numbere0165107
JournalPLoS One
Volume11
Issue number10
DOIs
StatePublished - Oct 1 2016
Externally publishedYes

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ASJC Scopus subject areas

  • Medicine(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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Sufit, A., Lee-Sherick, A. B., Deryckere, D., Rupji, M., Dwivedi, B., Varella-Garcia, M., Pierce, A. M., Kowalski, J., Wang, X., Frye, S. V., Earp, H. S., Keating, A. K., & Graham, D. K. (2016). MERTK inhibition induces polyploidy and promotes cell death and cellular senescence in glioblastoma multiforme. PLoS One, 11(10), [e0165107]. https://doi.org/10.1371/journal.pone.0165107